The present invention relates to a joint device and a motor.
Japanese Laid-Open Patent Publication No. 2002-364713 describes a prior art example of a motor in which a drive shaft of a motor body and a driven shaft (referred to as “worm shaft” in the publication) are coupled by a joint device so that the rotation generated by the motor body is transmitted from the drive shaft to the driven shaft by the joint device.
The above joint device includes a drive rotor fixed to the drive shaft of the motor body, a driven rotor fixed to the driven shaft, and a ring-shaped buffer (rubber member) located between the drive rotor and the driven rotor. The drive rotor and the driven rotor each include an engagement portion. The engagement portions project in an axial direction toward each other. The outer surface of the buffer includes a first engagement recess and a second engagement recess respectively receiving the drive engagement portion and the driven engagement portion. The drive engagement portion contacts the first engagement recess of the buffer in the rotation direction, and the driven engagement portion contacts the second engagement recess of the buffer in the rotation direction. This transmits a rotation force from the drive engagement portion to the driven engagement portion through the buffer. Thus, the buffer absorbs the impact produced when rotation is transmitted in the joint device.
However, if coupling tolerances result in misalignment between the drive shaft and the driven shaft, resistance that occurs between the drive engagement portion and the driven engagement portion in the joint device may hinder the smooth transmission of rotation. Although the above publication describes that the elasticity of the buffer allows for misalignment between the drive shaft and the driven shaft, rotation cannot be smoothly transmitted only by the elasticity of the buffer.